Manufacturing compound rolls



' whole cooling process and throughout Patented Sept. 13, 1938' PATENT OFFICE 2,129,683 MANUFACTURING COMPOUND ROLLS Hans Gontermann and Ferdinand Kiihn,

- Siegen, Germany No Drawing. Application January 14, 1936, Se

rial No. 59,158.

13 Claims.

In compound rolls it is known to. weld a hard outer sleeve which solidifies white and has a preponderantly' martensitic structure, special casting methods such, for example, as disclosed in Germant Patent 602,060, being used, to a softer core having pearlitic structure and which'solidifies grey. It has not been found possible so far in the-manufacture. of these rolls to avoid the very fine cracks which appear after cooling and which have usually been assumed to be due to tension effects These cracks still appear even when it is sought to adapt the shrinkage of the sleeve to that of the core.

Extensive researches have now proved that not only should the total expansion of the core, after the cooling of the roll from the casting temperature to the room temperature, be adapted to the total expansion of the sleeve, but that the variations in volume of the core and of the sleeve should-be adapted to each other throughout the each cooling stage; This can be achieved by so selecting the materials as to subject approximately equal portions of the substance of the core, and of the sleeve to the same critical transformations at the same intervals of time throughout the cooling.

This is effected in accordance with the invention by casting compound rolls having a sleeve of white martensitic structure and a core of cast iron alloy and aiming by suitable choice and proportioning of the constituents of the alloy to obtain a graphitic structure for the core which contains niartensitid mixed crystals in an amount corresponding to that in the sleeve structure. The term corresponding is to be construed as indicating that the amounts of martensitic mixed crystals in the core .and in the sleeve are such that-on microscopic observation of the two parts, an approximately similar total impression of the two grain structures is obtained. The existence of such correspondence in the cooled roll is evi-' dence of such inherent relation between the shell and core metals of the rollthat the expansions occurring on cooling which are bound ,up with the transformation in the solid state take place to approximately the same extent and at approximately the same time, sothat tension stresses between the core and the sleeve are avoided during the cooling or, at any rate, are so small that they can be borne by the sleeve without difficulty.

The described corestructure which is necessary for the manufacture of compound rolls can be made up in a known manner trom the most varied alloy materials by suitable proportioning.

the sleeve structure.

Germany January 16,

It,- for example,the material for the sleeve consists of an alloy containing Remainder iron and the usual impurities, then the core will preferably contain Percent Carbon 3.3 l.\ang'anese 10 Silicon u 3.5

Remainder iron and the usual impurities;

When a roll is cast with use of two suitable formulae such as those given above for the sleeve and the core of the roll, the sleeve structure then cools martensitically. The core alloy has martensitic mixed crystals in an amount corresponding to that in the sleeve structure. It is, however, suificiently tough silicon content, the carbon is not combined as iron carbide but is deposited as finely divided graphite. A suitable alloy which fulfills the above mentioned requirements may, for example,

' have the following composition:-

Percent Carbon 2- 3.5 Silicon 2- 5 Manganese Remainder iron and the usual impurities.

They can be run successfully on to practically all martensitic sleeve alloys. In addition to the characteristic content of carbon, silicon and manganese, the core alloy may also, however, contain 0.1 to 8% of nickel. An example of a composition suitable for a core alloy containing manganese and nickel is:

Percent Carbon- 3.3 Manganese 9 Nickel 0.8 Silicon; 3.0 Remainder iron and the usual impurities.

We claim:

1'. A compound roll having a martensitic white sleeve structure, and a softer core, comprising a core of cast iron alloy, the elements of which produce a casting which has a graphitic structure which contains martensitic mixed crystals in an amount substantially corresponding to that in because, owing to the high sleeve structure and a softer core, comprising a core made of an alloy containing 1 Percent Carbon 2- 3.5 Silicon 2- 5 Manganese 5-15 Remainder iron with the usual impurities 3. A compound roll having a martensitic white sleeve structure and a softer core, comprising a core made of' an alloy containing Remainder iron with the usual impurities.

4. A compound ferrous roll cast as a sleeve and core of diverse alloys, in which roll the sleeve alloy possesses in relative degree the characteristic of hardness and in which roll the core alloy possesses with relation to the roll sleeve the characteristic of machinability, the. two diverse ferrous constituents of the roll having in common martensitic grain structure of such correspondence that in the form of a one-piece roll-casting there is a minimum of tensile stresses in the zone of unification between' the diverse ferrous constituents of the roll.

5. A composite unitary roll 'casting as defined in claim 4, in which the softer roll core is substantially graphitic, that is, has substantially its entire carbon content in graphitic state.

6. A composite cast roll having a sleeve and a core of diverse ferrous alloys the unification between the roll sleeve and the roll core being that incident to the casting and solidification of the roll sleeve and core and subsequent simultaneous cooling each in the presence of the other and the unification between the roll sleeve and the roll core being approximately free from tensile stresses by virtue of the characteristic of their alloys to develop similar metallographic structures in cooling with corresponding approximately simultaneous expansion in both during passage through their critical transformation temperatures.

7. A composite roll which is made from a sleeve and a core of difierent iron alloys which have similar critical thermal charcteristics and which form a unitary body as a result of casting and congealing of the core and sleeve in contact with one another, the region of transition betweenthe 8. A method of manufacturing compound rolls having a martensitic white sleeve'structure and a softer core, comprising casting the core from cast iron alloy, the elements of which are chosen and proportioned so that the core hasagraphitic 2. A compound roll having a martensitic white structure which contains martensitic mixed' crystals in an amount corresponding to that in the sleeve structure.

9. A method of manufacturing compound rolls having a martensitic white sleeve structure and a softer core, comprising castingfthe core of the roll as an alloy containing Percent Carbon 2- 3.5 Silicon"- 2 5 Manganese 5-15 Remainder iron with the usual impurities.

- 10. A method of manufacturing compound rolls' having a martensitic white sleeve structure and a softer core, comprising casting the core of the roll as analloy containing Remainder iron with the usual impurities.

11. A cast iron compound roll comprising a sleeve of white martensitic structure, a softer cast iron'core containing graphitic carbon and having ametallographic structure approximating that of the sleeve in martensitic content, whereby the sleeve and core exhibit similar critical transformation phenomena, and a welded bond between the sleeve and core formed between the metals by solidification from the molten state in contact with each other; the roll being approximately free from cracks by virtue of said correspondence in the critical transformation phenomena in thessleeve and core.

12. A cast iron compound roll comprising a sleeve of white martensitic structure, a softer cast iron core containing graphitic carbon.

,manganese, and silicon, and having a metallosleeve of white martensitic structure, a softer cast iron core containing graphitic carbon, mang'anese, silicon and nickel, whereby the sleeve and core exhibit similar critical transformation phenomena,- and a welded bond between the sleeve. and core formed between the metals by solidification from the molten state in contact with each other; the roll being approximately free from cracks by virtue of said correspondence in the critical transformation phenomena in the sleeve and core.

HANS GONTERMANN. FERDINAND KI'iHN. 

